Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 202043 AFDILM AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 343 PM EST SAT DEC 20 2014 .SYNOPSIS... WEAK HIGH PRESSURE ALONG WITH A FRONT JUST OFFSHORE WILL KEEP CLOUDY AND COOL CONDITIONS IN PLACE THROUGH SUNDAY. ANOTHER ROUND OF RAIN IS EXPECTED EARLY MONDAY WHEN A STORM MOVES UP THE COAST. SHOWERS AND THUNDERSTORMS RETURN TUESDAY NIGHT INTO WEDNESDAY WITH A COLD FRONT. CLEAR WEATHER IS EXPECTED FOR CHRISTMAS DAY INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... AS OF 330 PM SATURDAY...REGIONAL RADAR AND SATELLITE SHOW BACK EDGE OF PRECIP SHIELD ENTERING THE WESTERN EDGES OF THE FORECAST AREA. DURING THE NEXT SEVERAL HOURS THIS DRYING WILL CONTINUE FROM WEST TO EAST...REACHING THE COAST DURING THE LATE AFTERNOON/EARLY EVENING TIME FRAME. THIS IS DOWN TO A SUBTLE BUT SIGNIFICANT SHIFT IN THE WINDS IN THE 2-4K FT AS THE WEAK SURFACE LOW SLOWLY MOVES AWAY FROM THE COAST. ALTHOUGH LOW LEVEL MOISTURE WILL LINGER OVERNIGHT THE LAYER ABOVE 800 MB DRIES OUT IN PART DUE TO DEEP WESTERLY FLOW. AT THE SURFACE THE WEDGE HOLDS ON WITH LOW LEVEL NORTHEAST FLOW MAINTAINING A STRATUS DECK THROUGH THE END OF THE PERIOD. ALTHOUGH MOISTURE BELOW 800 MB REMAINS ELEVATED FORECAST SOUNDINGS DO NOT SHOW ANY LAYER AS BEING SATURATED. WILL NOT CARRY ANY MENTION OF DRIZZLE BUT MAY MENTION FOG EARLY SUN MORNING. BOUNDARY LAYER WINDS DO NOT GO CALM BUT THEY WILL BE LIGHT. COMBINED WITH RECENT PRECIP THESE CONDITIONS COULD LEAD TO SOME PATCHY FOG DEVELOPMENT THOUGH LOWEST VIS WOULD BE ON THE ORDER OF 3 OR 4 MILES...SO DO NOT ANTICIPATE ISSUANCE OF DFA. LOWS END UP A LITTLE BELOW CLIMO...A COMBINATION OF HIGHS 10 DEGREES TODAY BELOW CLIMO...LIGHT NORTHEAST FLOW AND SUBTLE COLD ADVECTION BEHIND THE EXITING 5H SHORTWAVE. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... AS OF 330 PM SATURDAY...DREARY CONDITIONS WILL CONTINUE FOR THE SHORT TERM PERIOD. A BROAD SOUTHWEST FLOW ALOFT WILL INTERACT WITH A PERSISTENT BAROCLINIC ZONE JUST OFFSHORE AND A WEDGE OF HIGH PRESSURE INLAND. THE MODELS ARE IN GENERAL AGREEMENT ON SUNDAY REMAINING DRY FOR THE MOST PART. THERE COULD BE THE ISOLATED SPRINKLE OR MORE LIKELY PATCH OF DRIZZLE BUT OVERCAST SKIES AND COOL CONDITIONS SHOULD DO IT. A 300MB JET STREAK BRINGS ANOTHER ROUND OF RAIN FOR LATE SUNDAY INTO MONDAY MORNING. THE NAM AND GFS PAINT MOST OF THE HEAVIER QPF OFFSHORE WHERE THE BEST DIVERGENCE ALOFT RESIDES. THE BEST ISENTROPIC LIFT ON THE 300K SURFACE RESIDES WEST OF I-95 AND THE COAST IS LEFT IN BETWEEN WITH WEAK FORCING. HOWEVER THE QPF AMOUNTS WEST OF THE INTERSTATE ARE CERTAINLY NOT IMPRESSIVE MAKING THE OVERALL QPF AMOUNTS FAIRLY PALTRY. BEYOND MONDAY MORNING THE BEST FORCING MOVES OFF QUICKLY LEAVING OVERCAST/DRIZZLY SKIES. TEMPERATURE GUIDANCE IS IN GENERAL AGREEMENT OTHER THAN MONDAYS HIGHS WHEN THE GFS/MAV NUMBERS ARE MUCH WARMER. HARD TO TRUST THESE HOWEVER AS SURFACE PRESSURE PLOTS SHOW THE WEDGE...ALTHOUGH WEAKENING REMAINING IN PLACE. I DID USE A BLEND BUT WOULD NOT BE SURPRISED TO SEE SUBSEQUENT BULLETINS FROM THE GFS COOL. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 330 PM SATURDAY...WEDGE WILL BE ERODED ON TUES AS A WAVE OF LOW PRESSURE MOVES NORTH ALONG THE CAROLINA COAST. AT THE SAME TIME A HIGH AMPLITUDE MID TO UPPER TROUGH WILL DIG DOWN FROM THE UPPER GREAT LAKES INTO TEXAS PUSHING A COLD FRONT EAST. A DEEP S-SW FLOW WILL BRING PLENTY OF WARM AIR AND MOISTURE INTO THE SOUTHEAST AHEAD OF THE FRONT. INITIALLY ON TUES SHALLOW COOLER AIR WILL BE IN PLACE AS THE WARMER AIR OVERRIDES IT PRODUCING INCREASED ISENTROPIC LIFT AND INCREASED RAIN CHANCES. AS THE DAY WEARS ON...THE WINDS WILL COME AROUND WITH WARMER AND MOISTER AIR FLOWING IN. ALWAYS TOUGH TO TIME THIS AS COLD DENSE AIR HOLDS ON LONGER THAN MODELS USUALLY PREDICT. FOR NOW WILL KEEP WITH TEMPS WARMING THROUGH LATE DAY WITH WARMER AND MORE HUMID AIR MASS IN PLACE TUES NIGHT INTO WED. UNSETTLED WEATHER WILL REMAIN AHEAD THE COLD FRONT THROUGH TUES NIGHT INTO WED BEFORE COLD FRONT MOVES THROUGH LATE WED. INCREASING LOW LEVEL JET UP TO 40 KTS WILL COMBINE WITH BETTER UPPER LEVEL FORCING TO PRODUCE MORE WIDESPREAD SHOWERS THROUGH TUES NIGHT INTO WED. KEPT ISOLATED THUNDERSTORMS IN FORECAST TUES NIGHT INTO WED AS WARM FRONT LIFTS NORTH AND LOCAL AREA GETS INTO BEST MOISTURE AND LIFT. PCP WATER VALUES REACH UP TO 2 INCHES ALONG THE COAST WED AFTN THE DIGGING MID TO UPPER TROUGH WILL PUSH THE COLD FRONT THROUGH WED NIGHT BEFORE FINALLY MOVE OFF SHORE BY THURS MORNING LEAVING DRIER AND COOLER WEATHER FOR CHRISTMAS DAY. OVERALL EXPECT CLOUDY AND DAMP TO WET WEATHER THROUGH THE FIRST HALF OF THE PERIOD WITH COOLER MORE SEASONABLE WEATHER THURS INTO FRI AS HIGH PRESSURE BUILDS ACROSS THE SOUTH. THE HIGH WILL SHIFT OFF SHORE THROUGH FRI LEAVING A LIGHT RETURN FLOW AND WARMER TEMPS FRI INTO SATURDAY WITH A GOOD DEAL OF SUNSHINE. NEXT COLD FRONT SHOULD MOVE THROUGH SAT NIGHT BUT LOOKS LIKE IT MAY BE LACKING ANY DEEP MOISTURE. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... AS OF 18Z...RAIN WILL GRADUALLY END THIS AFTERNOON. GOOD CONFIDENCE IFR CONDITIONS WILL CONTINUE TO DEVELOP AND SPREAD ACROSS ALL TERMINALS THIS AFTERNOON. LEAST CONFIDENCE WILL BE KFLO/KLBT. IFR WILL CONTINUE INTO THIS EVENING EXCEPT EXPECT IMPROVEMENT TO MVFR AT KFLO/KLBT. AS WEAK HIGH PRESSURE DEVELOPS INTO THE COASTAL TERMINALS EXPECT MVFR CONDITIONS TO DEVELOP OVERNIGHT. VFR WILL DEVELOP AFTER SUNRISE WITH NE WINDS TO 8-12 KT. EXTENDED OUTLOOK...MVFR CIGS POSSIBLE ON SUN. RAIN LIKELY MON WITH MVFR/IFR CONDITIONS AS A COASTAL TROUGH DEVELOPS OFFSHORE. MORE SHOWERS/TEMPO MVFR EXPECTED TUE/WED AHEAD OF A STRONG COLD FRONT. VFR WITH GUSTY WINDS DURING THE DAY WED. VFR THURSDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 330 PM SATURDAY...NORTHEAST FLOW OF 10 TO 15 KT THIS AFTERNOON AND OVERNIGHT MAY BRIEFLY JUMP INTO THE 15 TO 20 KT RANGE AS GRADIENT TIGHTENS A BIT. EXIT OF SURFACE LOW TO THE EAST WILL BE FOLLOWED BY HIGH REASSERTING ITSELF SO GRADIENT DOES NOT CHANGE A LOT. 12 TO 18 HOUR PERIOD OF ENHANCED NORTHEAST FLOW WILL PUSH SEAS...CURRENTLY RUNNING 2 TO 3 FT...TO 3 TO 5 FT THIS EVENING AND OVERNIGHT. EXCEPTION WILL BE ALONG THE BRUNSWICK COAST WHERE OFFSHORE FLOW WILL KEEP SEAS 1 TO 2 FT CLOSER TO SHORE. ALTHOUGH CONDITIONS ARE LIKELY TO BE CLOSE TO SCEC ADVISORY DO NOT PLAN TO RAISE ONE AT THIS TIME. MAINLY BECAUSE THE INCREASE IN WIND SPEEDS SO FAR TODAY HAVE BEEN A LITTLE UNDER WHAT WAS EXPECTED. GIVEN THE ALREADY MARGINAL NATURE OF THE EVENT WILL HOLD OFF FOR NOW...THOUGH THE EVENING SHIFT MAY DECIDE TO RAISE ONE. SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 330 PM SATURDAY...A FAIRLY BRISK NORTHEAST FLOW WILL PERSIST ACROSS THE COASTAL WATERS SUNDAY IN BETWEEN A BAROCLINIC ZONE TO THE EAST AND HIGH PRESSURE INLAND. AS LOW PRESSURE DEVELOPS AND MOVES UP ALONG THIS FRONT SUNDAY NIGHT...THE FLOW WILL TURN MORE EASTERLY. SPEEDS THROUGHOUT WILL BE 15-20 KNOTS. SOME HIGHER SEAS CAN BE EXPECTED WITH THE SOMEWHAT PROLONGED NATURE OF THE WINDS...3-5 FEET. CANT RULE OUT A FEW SIX FOOTERS BUT THINK A SMALL CRAFT HEADLINE CAN BE AVOIDED. LIGHTER WINDS AND SEAS CAN BE EXPECTED MONDAY ALTHOUGH THE FLOW WILL GENERALLY BE THE SAME. LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 330 PM SATURDAY...WAVE OF LOW PRESSURE WILL MOVE UP THE CAROLINA COAST ON TUES WITH WINDS COMING AROUND THROUGH THE DAY. LIGHT NORTHERLY WINDS WILL SHIFT AROUND BECOMING MORE ON SHORE THROUGH THE DAY AND EVENTUALLY SOUTHERLY BY TUES EVENING. A LARGE AND POTENT STORM SYSTEM WILL PUSH A COLD FRONT EAST WITH INCREASING SOUTHERLY WINDS IN A TIGHTENING GRADIENT FLOW TUES NIGHT INTO WED. WINDS WILL INCREASE UP TO 15 TO 25 KTS TUES NIGHT INTO WED AHEAD OF THE COLD FRONT. THIS WILL PUSH SEAS UP FROM 2 TO 4 FT EARLY TUES TO 3 TO 5 FT BY LATE TUES. WNA SHOWS SEAS RAMPING UP ABOVE 6 FT BY WED MORNING AND POSSIBLE UP TO 7 TO 9 FT IN OUTER WATERS IN STRONGER SW TO W FLOW AS FRONT MOVES THROUGH THE WATERS LATE WED INTO WED NIGHT. EXPECT SMALL CRAFT CONDITIONS WED AND LASTING INTO THURS WITH HIGHEST SEAS GETTING PUSHED FARTHER OFF SHORE IN STRONGER W-NW FLOW BEHIND FRONT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...SHK NEAR TERM...III SHORT TERM...SHK LONG TERM...RGZ AVIATION...MRR

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